Gelling water-bearing explosives



United States atent 3,372,072 GELLING WATER-BEARING EXPLOSIVES Joseph D. Chrisp, Claymont, Del., assignor to E. L du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Sept. 16, 1966, Ser. No. 579,852 17 Claims. (Cl. 149-20) This invention relates to improvements in explosive compositions and, more particularly, to improvements in gelling aqueous explosives based on inorganic oxidizing salts.

The finding that explosives composed of an aqueous solution or suspension of inorganic oxidizing salt(s), at least partly soluble in water, together with one or more sensitizer or fuel components generally have greater work potential per unit weight than comparable compositions substantially free of water has led to the development of a variety of new blasting explosives in recent years. Among the sensitizer or fuel components commonly specified for use in such explosives have been the metallic and metalloid elements, mixtures, and alloys; one or more solid self-explosives such as TNT, pentaerythritol tetranitrate (PETN), cyclotrimethylenetrinitramine (RDX), nitrostarch, explosive grades of nitrocellulose or smokeless powders, etc.; and/ or one or more nonexplosive and generally carbonaceous combustibles, e.g., solid and liquid hydrocarbons and fractions, mono and dinitro substituted aromatics, powdered carbons and coals, crude and refined carbohydrate products, fatty acids and oils, organic amines, amides and hydroxy compounds, sulfur, etc.

While these aqueous solutions or slurry blasting agents have many advantages, including simplicity of manufacture and relatively low ingredient and production costs, there are several inherent problems involved in their storage and use. The compositions without modification tend to be more or less mobile fluids, a characteristic that can limit their use to substantially vertical boreholes unless the charges are in suitable fluid-tight packages. Segregation of the ingredients from the initially substantially uniform mixtures is an even more serious problem, in that separation of the charge components can lead to failures in initiation of detonation even when suitable primers are used or can result in failures in propagation of detonation through a column charge once initiation has occurred. Such segregation is accentuated by variations in the temperatures to which the charges are exposed in storage or in the boreholes and the concomitant changes in component solubility, particularly of the inorganic oxidizing salts, in the aqueous medium. A related situation exists in wet blast holes, where ground water can act to dilute the charges or leach their soluble components unless such charges are in fluid-tight containers, so that again failures in initiation or propagation can occur.

To overcome the foregoing problems, gelling agents or thickeners are commonly provided in the aqueous explosives. The thickeners usually employed are natural hydroxylated polymers, e.g., natural polysaccharide materials, often called gums, and their chemically modified derivatives, that swell in water or other aqueous media to form viscous colloidal solutions (sols) or mucilages. Among the polysaccharides and derivatives, the galactomannan gums, locust bean gum and especially guar gum, most commonly are used as thickening or gelling agents. These thickeners tend to immobilize the insoluble and undissolved soluble components, so that segregation is minimized. They also aid in protecting the soluble components from extraction by external water sources. They further permit wide variations in the consistency and fluidity of the aqueous explosives, which can range from fluids that can be pumped by slurry trucks, to thick, rigid or flexible masses, suitably transferred by extrusion or similar methods. Additional variation in the type and extent of thickening or gelling action has been accomplished by use of appropriate crosslinking agents, e.g., borax, for the hydroxylated polymer-thickeners. The best of such crosslinking agents, in addition to permitting close control of product consistency, also serves to protect the polysaccharide molecules against hydrolytic degradation and bacterial attack, so that the product maintains its initial physical and explosive characteristics over long periods of time, even under conditions of elevated temperature, e.g., of F. or above. However, gelling systems based on the galactomannan gelling agents, particularly guar gum, have not proved entirely ideal. For example, such gelling systems often require careful control of pH during formulation in order to produce gel structures which remain stable over periods of several months or more. When storage is to be under heated conditions, e.g., at 100 F. and above, the lack of stability of such galactomannan systems commonly employed (borax crosslinked) is even more apparent. Still further, stable pourable, relatively-thin blasting compositions cannot be prepared using crosslinked guar gum as the gelling agent without significantly reducing water resistance of the product, particularly after storage, to such an extent that, in wet boreholes, soluble components are easily leached away. Recently, there has been increasing elfort to provide such pourable, water-resistant compositions since compositions of this nature offer advantages of ease in loading and handling by manual means to the small operators; these properties have heretofore been available only with slurry trucks. With the currently used gelling systems, however, this has not been achievable.

Accordingly, there is still a need for a gelling system for water-containing blasting compositions which can be used in a wide range of water-containing explosive compositions to give stable products ranging from pourable, yet cohesive, water-resistant gels to rigid, firm cohesive gels. This invention fills such a need.

This invention provides an improvement in the process for making water-bearing explosives which comprises bringing together water, fuel and an oxidizing component consisting essentially of inorganic oxidizing salt, such improvement comprising gelling the aqueous phase of said explosives by copolymerizing in situ a mixture of monoand polyethylenically unsaturated monomers soluble and stable in the system, said mixture comprising:

(a) About from 0.3% to 10% and preferably 0.5 to 5% by weight, based on the aqueous phase of the composition of monomer selected from at least one of the group consisting of (l) monomers of the formula where R is hydrogen, lower alkyl, or hydroxyalkyl of 1 to 4 and preferably 1 to 2 carbon atoms, X is COOH,

' M being alkali metal or ammonium, and (2) soluble salts (b) is at least one monomer of the formula [A] Y where A is selected from R o R CHz=( 3-( OH2=-OH2- and CI-I =CH, the Rs are the same or different and are chosen from the group set forth above for monomer (a), n is 2 to 4, inclusive, preferably 2 or 3, and Y is a bridging radical to which a plurality of the unsaturated moieties, A, are bonded by oxygen or nitrogen atoms. Y can be simply oxygen or nitrogen, but preferably consists of carbon and hydrogen atoms alone or together with oxygen linked to a through terminal O,

or N wherein N is a member of a heterocyclic ring. A primary requirement of Y is that it be stable in the system and not insolubilize (b).

In situ polymerization as used herein means that the polymerization is carried out in the presence of substantially all of the constituents of the aqueous phase of the ultimate explosive composition.

The monomers, and particularly the monoethylenically unsaturated monomer, used in gelling the aqueous phase of water-containing blasting agents in accordance with this invention must have appreciable solubility at ambient temperature (20-25 C.) in the particularly aqueous solution of inorganic oxidizing salt being employed at least within the aforesaid ranges. Furthermore, the monomer must form in the said aqueous phase homopolymers which will not be removed, e.g., by precipitation, from the aqueous phase nor agglomerate into fiocculates or lumps. Copolymerization forms a crosslinked structure which is a gel rather than a solid precipitate. This gelled structure swells in the aqueous phase of the blasting composition holding the aqueous phase and is of substantially constant composition throughout. The gelled crosslinked structure contains a fairly low ratio of polymer solids to liquid phase, e.g., less than about 1:5, this ratio being roughly equal to the weight ratio of monomers to other components making up the liquid phase, in contrast to precipitates or agglomerates in which there is a relatively high ratio of polymer solids to liquid phase.

Reference to stability unless otherwise indicated refers to the absence of significant degradation of monomers or their polymerization products, in the aqueous phase of the blasting composition involved. Since prolonged stability is commonly of significance in gelled blasting compositions, stability refers particularly to the absence of appreciable degradation in copolymer containing samples when they are subjected to accelerated thermal stability tests involving heating of the material in question in the aqueous solution of oxidizing salt at temperatures of about 100 F., for example, for 8 to 12 hours.

Broadly, the improvement of this invention can be applied to any of the known general types of water-bearing explosive compositions. Prefer-ably, the compositions of this invention comprise at least one water-soluble, inorganic oxidizing salt, about from to 45% and preferably to 30% of water, based on the total weight of composition, and about from 0.1 to 5%, by weight of the composition of the in situ formed gelling system of this invention. The compositions of this invention also can contain, by weight, up to about 50% of a metal fuel, up to about 40% of a solid organic explosive sensitizer and up to about 25% of a non-explosive, preferably carbonaceous, fuel, the compositions having an oxygen balance of about from -25 to +10% and preferably about from -10 to 0%.

Examples of monoethylenically unsaturated monomers which are suitable for use in accordance with this invention from the viewpoint of solubility and accordingly dispersability in the aqueous phase of water-containing blasting compositions and availability at reasonable costv include amides such as acrylamide, methacryl mide an N-methylacrylamide and hydroxyalkyl derivatives such as 04,2 hydroxyethylacrylamide and a hydroxymethylacrylamide; acids such as acrylic acid and methacrylic acid; salts of acrylic acid such as sodium, potassium or ammonium acrylate; and soluble salts of monovinylpyridines, particularly and preferably the nitrate salts of the 4-vinylpyridine. Acrylamide is the particularly preferred monomer because of its low cost and rapid polymerization in the aqueous phase of the blasting compositions. Usually, the concentration of acrylamide used ranges from 0.3 to 10% and especially from 0.5 to 5%.

With some monomers, particularly the monovinyl pyridines, it is usually necessary to form a soluble salt, e.g., of an acid, such as acetic acid, sulfuric acid, phosphoric acid, perchloric acid, and particularly of nitric acid, to impart solubility in the aqueous phase of the blasting composition. This can readily be accomplished by adding the mineral acid to the blasting agent at the same time the monoethylenically unsaturated monomer, viz, the monovinylpyridine, is added, the liquid and chemical make-up of the added acid being considered in calculating the percentage composition and oxygen balance of the explosive composition. Nitric acid contributes to the explosive energy of the composition, adds no foreign anions and hence is particularly preferred in preparing a soluble salt. Acrylic acid and the alkali metal and ammonium salts thereof and acrylamide do not require addition of solubilizing acid. Acrylic acid is particularly useful in compositions in which the concentration of inorganic oxidizing salt in the aqueous phase does not exceed about 55%. Acrylamide is soluble over a wide range of concentrations of inorganic oxidizing salt, e.g., concentrations of up to 75% or more.

Representative polyunsaturated monomers that can be used in this invention include one or more of polyfunctional acrylic compounds such as acrylic amides, for example, N,N' methylenebisacrylamide, trimethylenebisacrylamide, hexamethylenebisacrylamide, N,N' methyl enebismethacrylamide, N,N,'N" triacrylhexahydro-s-triazine, acrylic and methacrylic acid esters, including mixed esters of polyols such as glycerin, sorbitol, mannitol, and pentaerythritol, for example, ethyleneglycol, dimethacrylate, tetramethyleneglycol, dimethacrylate, trimethylolpropane trimethylacrylate; mixed acrylic-allyl compounds such as allyl acrylate, N-allylacrylamide and allyl methacrylamide, polyfunctional allyl compounds such as diallylamine, the diallyl ether of pentaerythritol, and N,N-diallyladipamide, polyfunctional vinyl compounds such as divinyl adipate, divinyl succinate, divinyl maleate, and divinyl malonate; and mixed vinyl acrylic compounds such as vinyl acrylate and vinyl methacrylate.

Of the aforementioned polyfunctional monomers those in which A is acryl and bridging radical Y bears terminal oxygen or amido nitrogen joined by at least one alkylidene radical are preferred because of optimum physical properties of products formed therewith and their availability at low cost. Of these, N,N-methylenebisacrylamide, N,Nmethylenebismethacrylamide and hexamethylenebisacrylamide are particularly preferred. As discussed below, N,N'-methylenebisacrylamide can conveniently be prepared conjointly with acrylamide in proportions stoichiometrically needed for forming gels during the hydrolysis of acrylonitrile in the presence of mineral acid and thus represents a particularly preferred polyethylenically unsaturated monomer for gelling blasting agents at low cost.

Both the choice of monomers employed for in situ copolymerization and the concentrations of these components are influenced by the concentration of the inorganic nitrate salt in the aqueous phase and by the intended end use of the resulting gelled compositions. In general, the concentration of monomers increases with concentration of water in the aqueous phase. The particular poly functional monomer used depends to some extent on the monofunctional monomer used. The polyfunctional monomer should polymerize sufficiently rapidly with respect to the monofunctional monomer so that, e.g., homopolymerization of the monofunctional monomer does not run substantially to completion before copolymen'zation begins. Stated differently, the monoand polyfunctionally unsaturated components are chosen so that they have roughly similar polymerization rates under the reaction conditions employed.

The aqueous phase of the blasting composition is converted from a liquid, water-like consistency to a gel char acterized by the presence of an aqueous phase and a solid phase substantially uniformly distributed or dispersed therein. The gels are substantially homogeneous down to substantially colloidal dimensions and resist finite shear forces. Thus, the copolymerization products form a continuous or semicontinuous matrix in the gelled compositions, at least a portion of the continuity being due to crosslinking of polymer chains by the polyethylenically unsaturated monomers which, owing to their polyfunctionality are capable of reacting at two or more sites in the molecule. A broad spectrum of product consistencies is readily available varying from pourable, cohesive, water-resistant masses to moderately stiff or very stiff gelatin-like masses, that often are resilient, elastic and even rigid, shapable products. For satisfactory gel formation, the concentration of the monoethylenically unsaturated monomer component used in forming the copolymerization products usually will constitute at least about 0.3% by weight of the aqueous phase, although in some cases somewhat lower concentrations can be effective. Higher minimum concentrations similarly can be desirable, depending on the concentration of inorganic oxidizing salt in the aqueous phase, the particular monomers employed, and the presence of other dissolved or suspended components in the gelled compositions. On the other hand, the concentration of the monoethylenically unsaturated monomer component usually does not exceed about by weight, of the aqueous phase since even Where solubility considerations permit higher concentrations, the resulting gelled compositions are not materially improved thereby.

In comparison to the monoethylenically unsaturated monomers, only reatively minor proportions of the polyethylenically unsaturated monomer components are required to form gelled products of satisfactory consistencies and stabilities. About from 1 to 30% by Weight of the polyethylenically unsaturated monomer, with reference to the monoethylenically unsaturated monomer(s), generally is used. Again, the exact concentrations are influenced by the factors enumerated above for the monoethylenically unsaturated monomer component and also by the particular polyethylenically unsaturated monomer chosen. In general, about from 2 to 10% by weight of polyethylenically unsaturated monomer will be used based on the weight of monoethylenically unsaturated monomer.

The monomers employed for in situ polymerization in the gelled explosive compositions of this invention need not be highly purified. For example, crude acrylamide sulfate obtained by the hydrolysis of the corresponding ni trile, acrylonitrile, in the presence of concentrated mineral acid, e.g., sulfuric acid, can be used directly without purification. Also, if desired, at least a portion of the polyunsaturated monomer, e.g., methylenebisacrylamide sulfate, can be formed in the same crude hydrolysis mixture, for example, by adding an aldehyde such as formaldehyde thereto in the proportion stoichiometrically necessary to yield the desired quantity of polyethylenically unsaturated monomer.

The reaction mixture used in preparing the gelled compositions of this invention also contains free-radical polymerization promoter(s) or initiator(s) which are soluble to the extent of at least about 0.1%, by weight, in the aqueous phase. Suitable promoters includes sodium,

potassium and ammonium salts of inorganic peracids such as persulfates, perborates and pervanadates; hydrogen peroxide; and organic peroxide and azo catalysts such as azobis (isobutyronitrile), a,a'-azobis (agy-dimethyl-ymethoxyvaleronitrile) tertiary butyl hydroperoxide, methylvinyl ketone peroxide, benzoyl peroxide and peracetic acid. Persulfates are usually preferred. Redox systems that utilize a source of persulfate ion 0,?) as one component can be suitable throughout a range of concentrations of inorganic oxidizing salts. The persulfate ions which are introduced as a soluble persulfate salt, can be used alone in the solution of inorganic oxidizing salt to promote the copolymerization reaction or an added reducing agent can also be employed to form a redox couple. Reducing agents that can also be used if desired include nitrogen bases such as hydroxylamine, carbohydrazide, and, particularly hydrazine. If needed, higher rates of polymerization are achieved at lower temperatures when the polymerization system also includes a minor amount of metal ion, usually a Group IB metal ion. These metal ions are introduced as soluble inorganic or organic salts, e.g., as the nitrates, sulfates, or acetates. Other useful persulfate couples are HSO -[S O F and Fe+ -[S O and S O -[S O and nitro-tris-propionamide-[S O In general, the total amourit of promotor used varies with the particular promoter and monomers, and increases proportionately with the desired speed of polymerization, but usually is at least 0.002% and preferably within the range of about from 0.002 to 3% based on the total weight of aqueous phase containing monomers to be polymerized, large excesses of promoter having no detrimental effect on the gel structure. The optimum concentration of the preferred persulfate ions, based on total monomers, i.e., both monoand polyethylenically unsaturated, can vary considerably depending on the particular polymerization system, the desired consistency of the gel, and the presence or absence of supplementary promoter components, but in general will be about from 0.005 to 2% by weight of the aqueous phase.

Preparation of the gelled compositions of this invention can be accomplished by simply incorporating the monoand polyethylenically unsaturated monomers into a solution of the inorganic oxidizing salt, preferably at elevated temperatures of e.g., about 50 to C., followed by addition of the polymerization promoter(s). In some cases, the monomers can first be dissolved in a small amount of water; such water of course is considered in determining the concentration of the solution of inorganic oxidizing salt comprising the majority of the aqueous phase of the explosive composition. In the preparation of the blasting compositions it is particularly convenient to use concentrated aqueous solutions of ammonium nitrate commonly known in the art as ammonium nitrate liquor, the aqueous phase of the gel matrix being provided for the most part by the water in this solution. Other ingredients of the blasting composition are added to this liquor, including the mixture of monoand polyethylenically unsaturated monomers, and the polymerization promoter added last. Care should be taken that all ingredients are uniformly dispersed prior to the addition of polymerization promoter. Agitation used for blending of components usually is continued until after the composition is gelled, particularly when added fuels or sensitizers are solids, e.g. TNT, ferrophosporus, ferrosilicon, aluminum, and the like which must be distributed uniformly throughout the gel matrix. In some instances, e.g., when the composition is to contain a high percentage of solids, e.g, TNT, or fuels which inhibit polymerization are to be incorporated in the compositions, all ingredients except such additives can be mixed and gelled and such additives blended with the finished gel.

The rate of polymerization and in some instances, product consistency, can be adversely affected by the presence of nitrogen oxides and oxygen, either in dissolved form or as the gases, and by the presence of large amounts of compounds conventionally used to inhibit free-radical polymerizations of the monomers. Compensations for these variations can be provided, when necessary, by increasing the concentrations of polymerization promoters. An alternative and generally more economical expedient, however, is to reduce the concentrations of these polymerization-retarding components prior to the polymerization. In the case of nitrogen oxides and oxygen, this can be accomplished by carrying the polymerization out under a blanket of an inert gas, typically nitrogen. To further eliminate polymerization inhibiting concentrations of nitrogen oxides and/ or oxygen the components of the blasting composition, particularly the aqueous solution of inorganic oxidizing salt, can be sparged with the inert gas.

As stated earlier, the compositions of this invention usually contain at least about 20% by weight of an inorganic oxidizing salt. Any of the conventional salts used in explosives including ammonium, alkali metal and alkaline earth metal nitrates, chromates, dichromates, chlorates, and perchlorates, as well as mixtures of two or more such salts can be used in the compositions of this invention. Examples of these salts are ammonium nitrate, ammonium perchlorate, ammonium chromate, ammonium dichromate, ammonium chlorate, sodium nitrate, sodium perchlorate, potassium nitrate, potassium perchlorate, potassium dichromate, magnesium nitrate, magnesium perchlorate, and calcium nitrate. Preferably, the inorganic oxidizing salt contains at least 65% of at least one salt which is highly soluble in water at room temperature, i.e., at least as soluble as ammonium nitrate, and preferably the aqueous phase in the compositions contains a substantial proportion of oxidizing salt, e.g., 40 to 70% by weight thereof. Inorganic oxidizing salt mixtures containing at least about 50% by weight of ammonium nitrate and at least about by weight of sodium nitrate are particularly preferred. The composition of this invention contains about 5% to 45% by weight of water, and preferably to 30% of water.

To impart fluidity to the water-bearing gelled explosive compositions, particularly at temperatures of lower than about 10 F., the composition can contain about from 0.25 to 10%, and preferably about 1 to 5%, by weight, based on the total composition, of a winter fiuidizing (antifreezing) agent as described in US. Patent 3,190,777, the teachings of which are to be included in this application by reference. Examples of suitable fiuidizing agents are methanol, formamide, dimethyl sulfoxide and methyl Cellosolve. These fiuidizing agents can be considered as a portion of the fuel contained in the composition.

Various self-explosive fuels or non-explosive carbonaceous fuels or various combinations of mixtures of these types of fuels can also be present. The fuel or fuels used in the compositions of this invention can be varied widely provided that the fuel is stable, i.e., chemically inert with the system in which it is employed, during preparation and storage prior to detonation. Self-explosive fuel refers to a substance which by itself is generally recognized in the art as an explosive. Examples of self-explosive fuels include organic nitro compounds, nitrates and nitramines, such as TNT, dinitrotoluene, pentaerythritol tetranitrate (PETN), tetranitromethylaniline (tetryl), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), nitrostarch, explosive-grade nitrocellulose, smokeless powder, and mixtures of such explosives, e.g., pentolite (PETN/TNT), Composition B or cyclotol (RDX/TNT), and tetrytol (tetryl/TNT). For economic reasons, TNT alone or incombination with other self-explosive fuels is preferred for use in the compositions of this invention. The TNT or its mixtures can be introduced into the compositions in the form of crystals, grains, pellets, flakes or any other particulate form which allows ready dispersion thereof. In general, up to 50% and, preferably, 10 to 45% by weight, based on weight of the composition, of self-explosive fuel is used.

Examples of nonexplosive fuels which can be present include sulfurous fuels including sulfur itself and siliceous fuels and carbonaceous fuels. Examples of carbonaceous fuels which are preferred are finely divided coal and other forms of finely divided carbon, solid carbonaceous vegetable products such as starch, ivory nut meal, wood and paper pulps, sugar, bagasse and the like; solid and liquid organic hydrocarbons such as powdered paraffin waxes and fuel oils; fatty oils; vegetable oils; and mixtures of two or more of the foregoing carbonaceous nonexplosive fuels. In general, up to 25% and preferably, about fro-m 2 to 20% by weight of such carbonaceous fuels are used. Up to about 10% of sulfur-ous fuels and up to about 5% of siliceous fuels are generally used.

The metallic fuels which can be present in accordance with this invention include, for example, light elements such as aluminum, magnesium, zinc, boron and silicon both singly and in combination, and heavier metallic alloys including ferrophosphorus and ferrosilicon, as well as mixtures of two or more of these metals or alloys. A preformed coating, e.g., of fatty acid and high viscosity oil, can be provided on particles of any of these types of metallic fuels. Such a coating has been found of particular benefit for use with light elements and alloys thereof with minor amounts of each other and, for example, iron, manganese, silicon, copper, zinc or chromium, whose composition and degree of purity varies markedly from lot to lot.

The quantity of metallic fuel used in the compositions of this invention naturally varies with the particular fuel employed and can constitute up to 50% by weight of the total composition. When the metallic fuel is aluminum, usually about from 1 to 25% by weight is used Whereas with heavier metallic fuels, such as ferrophosphorus and ferrosilicon, about from 10 to 30% by weight is used. The average particle size of the metals can vary, for example from 325 mesh to +15 mesh, but preferably is on the order of to 18 mesh.

The total weight of fuel, i.e., the weight of the combination of metallic, carbonaceous and/ or self explosive fuel, usually is adjusted so that the total com-position has an oxygen balance of about from 30 to +10%, and excepting for those combinations containing the heavier metallic fuels such as ferrophosphorus and ferrosilicon, the oxygen balance is preferably between about 10 to 0%.

In the following detailed examples, parts and percentages are by weight unless otherwise indicated.

In the following examples, the terms noted describing the product characteristics designate the following:

Very firm viscosity of about from 3 million to 10 million centipoises as measured with a TF (1) spindle at 0.5 r.p.m. (1) on the Brookfield Syn chroelectnc Viscometer.

Firmviscosity of about from 1 million to 3 million centipoises measured with a TE (1) spindle at 1.0 rpm. (1) on a Brookfield Synchro-lectric Viscometer, Model RVT, with helipath attachment.

Medium firmviscosity of about from 400,000 to 1 :million centipoises using the same conditions of measurement on the Viscometer.

Weakviscosities generally less than about 400,000 centipoises, (1) Change in spindle and r.p.m. needed to obtain accurate readings, generally 200,000 to 400,000 centipoises.

' Examples 1-33 Gelled aqueous solutions of inorganic oxidizing salts are prepared from the materials noted in Table I, these aqueous solutions being suitable for providing the aqueous phase of a blasting composition. In preparing the gelled compositions, the monoand polyunsaturated monomers, together with acid as noted, are dissolved in the aqueous solution of inorganic oxidizing salt at the temperature indicated. Next, the promoter system indicated 9 is added and mixing continued until polymerization is substantially complete. In the promoter system, [S is added as aqueous solution of ammonium persulfate (20-50% concentration, by weight), other promoters being added as the compound noted. Gelation time refers Example 34 An explosive composition in which the aqueous phase is gelled by the in situ for-med polymerization product of acrylamide and N,N'-methylenebisacrylamide is prepared as follows.

to the time expired between the addit1on of the promoter To 65% ammomum filtrate hquor at are added System to the reactlfm fnlXtum andthe first afipeafance sodium nitrate and a premixed blend of acrylamide and of gelled copolymerization product in the reaction mass. N,N'-me[hy1enebi5acry1amide Mi i i begun d The gels are observed at the temperature indicated; most tlnued about three minutes to assure uniform dispersion of the gels tend to become firmer as they cool to ambient 10 of ingredients. A 50% aqueous solution of ammonium room temperature. None of the gel products show visible persulfate (as promoter) is then added. After gel formaindication of deterioration at ambient temperatures over tion is observed, i.e., about two minutes, pellets of TNT times of a week or more, the maximum period of obare added and blended into the gelled composition until servation. complete incorporation and dispersion thereof is observed.

TABLE'I Monomers Inorganic Oxidiz- Promoter, percent of Temp., Product Characteristic, Ex. ing Salt, percent (a) Monoethylemcally (b) Polyethylemcally aqueous soln. 0. Gel Time in aq. soln. unsatd. monomer, unsatd. monomer,

percent of aq. soln. percent of monomer (a) 1.. NH4NO3, 65%... Acrylamide, 2% N,N I n g n 5 ry1- (82010- 0.1% 60 Medium firm gel, 1 min.

ami e 2. NH NO 65% Acrylamide sulfate, N,N-methylenebisacryl- (3209- 0.1% 60 Firm gel in 1 min.

crude 7% (=2.65% amide, 5.5%. acrylamide) 3..--- NHrNOz, 65%...- Acrylic acid, 4% N,N r net l 7y1eneb1 a ry1- 2 9, 0.1% 60 Medium firm gel in 2 min.

amr e 4"--- NH4NO3, 65%..-- 4-vir11y1pyridine, nitrate N,N:(met5h% l7enebisacryl- (5209- 0.1% 60 Firm gel in 95 sec.

- sat 7 ami e, 5 NH4NO3, 65%.... Acrylamide, 2% N,N tdrirre /thylenebisacryl (8209- 0.1% 60 Medium firm gel in 6 min.

ami e 6....- NHiNoa, 65%...- Acrylamide, 3% N,NQriigeggylenebisacryl- (8209- 0.1% 60 Firm gel in 42 see.

ami e, 7 NH NO3, 65%...- .do N,N hexamethyl nebis- ($209, 0.1% 60 Firm gel in 50 see.

aorylamide, 6.6%. 8 NH4NO3, 65%...- Acrylamide, 2% N,N-lliexarretgglenebis- (8105), 0.1% 60 Weak gel in 7 min.

acry anu e, 9 NH NO3, 65%...- Acrylamide, 3% Allyl acrylate, 13% (8209- 0.1% 60 Medium firm gel in 144 sec. 10...- NH NO3, 65%...- Acrylamide, 4% Allylmethacrylamlde,20%. (8209- 0.1% 60 Firm gel in 1 min. 11 NH NO3, 65%.... --...do Diallyilgtger oi pentaeryth- (S2Os) 0.1% 60 Firm gel in 6 min.

ri o 0 12.--- NH4NO3, 65%...- -....do Diall glagngne (asuNoi (slow- 0.1% e0 Firm gel in 160 S60.

salt 0 13..-- NHlNOQ, 65%.... ...do N,N-dially ladipamide, (egos- 0.1% so Mgdium firm, elastic gel in mm. 14...- NH4NO3, 65%...- do N-allylacrylamide, 20%--.- ($208), 0.1% 60 Firm gel in 1 min. 15 NHqNOz, 65%..-- Acrylamide, 3% N,N -netil 17ylenebisacryl- H202, 0.12% 60 Firm gel in 3 min.

arm e, 16. NH4NO3, 65%...- -.-.do do 0 Tert-butyl hydrogen 60 Weak gel in 5 min.

peroxide, 0.4%. 17..-- NHqNOa, 65%..-- Acrylamide, 4% N,N-(r1nethylenehisacryl- Benzoyl peroxide, 0.4%. 70 Firm gel in 10 min.

arni e 7 18 NHQNOQ, 65% ..do --..do.. Methylethyl ketone 50 Firm gel in 6 min.

peroxide, 0.4%. 19-.-- NH4NO3, 65% --do ...do Agoinswutyronitrile), 70 Firm gel in 100 sec. 20-..- NHlNOa, 65%.... Acrylanu'de, 2.5% N,N -netgglenebisacryl- (8 09 0.7% 70 Medium firm gel in 12 sec.

ami e, 21...- Ca.(NOs)2, 9%.-- Acrylamide, 2% N,N -(11net6l i7lenebisacry1 ($205), 0.1% 60 Medium firm gel in 21 sec.

ami e, 22..-- NH4NO3, 65%..-- Acrylamide, 3.0% Triatgs ilhealydrotriazine, (5205- 0.1% 60 Firm gel in 1 min.

(A .6 23...- NH4NO3, 65%..-- Acrylamide, 2.0% AH'I, 6%... (8200- 0.1% 60 Medium firm gel in 1.5 min. 24..-- NH4NO3, 65%...- Acrylamide, 3% Allyl acrylate, 6.7% 50 Very firm gel in 38 sec. 25...- NHiNOa, 65%.... Allyl methacrylamide, 10%. 50 Very firm gel in sec. 26..-- NHiNO3, 65%...- Acrylamide, 4% Vinyl metliacrylate, 10%... Firm gel in 72 sec. 27..-- NH4NO3, 0 Trimeithyloll propa ryie tri- (8209*, 0.8% 50 Medium firm gel in 20 sec.

met acry ate l0 28 NH4NO3, 65% --d0 Ethyltin? glggfyol din ieth- ($209, 2.0% 50 Medium firm gel in 124 sec.

acry a e, 29 N aNOg, 17%.--. Aerylamide, 1.25%..--- N,N-(rlnethyenebisacryl- (8209- 0.2% Weak gel in 84 sec.

ami e 7.5 30-..- NH4NO3, 65%.... Acrylamide, 1.5% N,N-(r1net1hygnebisacryl- (SzOrW, 0.07% 70 Weak gel in 450 sec.

ami e .5 31..-- NH4NO 65%..-- ----do ..do a (slow, 0.02% 50 Weak gel in 800 see. 32 N H4NO3, 65%...- Acrylamide, 1% N,N'-metl 7ylenebisacryl- (8 09- 1.0% 50 Medium firm gel in 184 sec.

amide 5 33 NHNO3, 70%.... -.-.do N,N-metl1lenebisacryl- (8208), 0.016% 50 Firm gel in 19 sec.

amide, 10%.

1 Monomers are stored in solution of inorganic nitrates for 96 hrs. at 70 C. before initiators are added.

Similar results are obtained when ammonium nitrate solutions are gelled by the in situ polymerization of am monium acrylate and Z-hydroxymethacrylamide, each with N,N'-methylenebisacrylamide in the general amounts and procedure shown above, using (5 09- as the promoter. In a like manner, similar results are also obtained when the monoethylenically unsaturated monomer is acrylamide and the polyethylenically unsaturated monomer is each of divinyladipate, divinylsuccinate, and divinylmaleate, also using (S2Og) as the promoter.

The gelled aqueous compositions described above are converted to explosive compositions by blending each with TNT in an 70/30 weight ratio.

Percent 65% ammonium nitrate liquor 50 Sodium nitrate 20 Pelleted TNT 30 1 Arcadian sodium nitrate commercially available from Monsanto Chemical Corp.

The composition also contains, by hundred weight, 0.75 part acrylamide (approximately 1.5% of the aqueous phase), 0.05 part methylenebisacrylamide, and 0.17 part ammonium persulfate.

The finished composition is a pourable, water-resistant gel having a viscosity of about 100,000 to 400,000 c.p.s., and is suitable for use in water-filled boreholes.

When initiated by two conventional boosters, each comprising 1 lb. (454 g.) of cast TNT, the composition detonates at 4900 m./sec. in air at ambient temperature of 85 F. (30 C.).

When similar compositions are prepared in which the amounts of acrylamide and methylenebisacrylamide are increased by 50%, more viscous water-resistant gels are obtained, the viscosities of these gels being about 1 to 4 million, i.e., firm gels.

Example 35 An explosive composition of the formulation shown below is prepared based on the gelation of the aqueous phase of the formulation by the copolymerization product of acrylamide and N,N-methylenebisacrylamide effected in the presence of (S O The composition is prepared, under a nitrogen blanket as in Example 34, by dispersing sodium nitrate, a premixed blend of monomers, and the solid fuels, aluminum and coil, in 65% ammonium nitrate liquor at 54 C., then adding a 50% aqueous solution of ammonium persulfate as promoter. The ammonium nitrate liquor is sparged with nitrogen as the ingredients are added. Gel formation is observed in about 2 minutes.

The soft gel formed is of a weak-to-medium firm consistency. When initiated by two commercial boosters, each comprising 1 1b. (454 g.) of cast TNT, the composition detonates at 4500 m./sec. in 3-inch diameter at 85 F. (30

1 Arcadian sodium nitrate commercially available from Monsanto Chemical Corp.

Approximately 3%, by weight, of the aqueous phase.

I claim:

1. In the process for making water-bearing explosives which comprises bringing together water, fuel and an oxidizing component consisting essentially of inorganic oxidizing salt, the improvement which comprises gelling the aqueous phase of said explosives by copolymerizing in situ a mixture of monoand polyethylenically unsaturated monomers soluble and stable in the system, said mixture comprising:

(a) about from 0.3 to by weight, based on the aqueous phase of monomer selected from at least one of the group consisting of (1) monomers having the formula wherein R is hydrogen, lower alkyl or hydroxyalkyl of up to 4 carbons, inclusive, X is COOH,

where M is alkali metal or ammonium, and (2) soluble salts of monovinyl pyridines; and

12 (b) about from 1 to 30%, based on the weight of (a) of polyethylenically unsaturated monomer polymerizable with (a) having at least two terminal methylene groups. 2. A process of claim 1 wherein (a) is at least one monomer of the formula CHFC-X and (b) is at least one monomer of the formula [A],,Y wherein A is selected from at least one of the group consisting of and CH CH--, the Rs being chosen independently from the same group as in (a); Y is a bridging radical to which a plurality of A moieties are bonded by oxygen or nitrogen in Y and n is 2 to 4, inclusive.

3. A process of claim 2 wherein in (b) A is n is 2 to 3 inclusive, Y is an aliphatic chain of 1 to 6 carbons to which the A moieties are joined by amido nitrogen or by oxygen, and the Rs in the (a) and (b) components are hydrogen or methyl.

4. A process of claim 3 wherein the (a) component consists essentially of acrylamide.

5. A process of claim 4 wherein the ([1) component consists essentially of N,N-methylenebisacrylamide.

6. A process of claim 3 wherein said copolyrnerization r is promoted with a free-radical initiator.

7. A process of claim 6 wherein said free-radical initiator comprises persulfate ion.

8. A process of claim 7 wherein said copolymerization reaction mixture also contains hydrazine.

9. A process of claim 6 wherein said copolymerization is additionally promoted with Group IB metal ions.

10. In water-bearing explosives comprising fuel, water and an oxidizing component consisting essentially of inorganic oxidizing salt, the improvement which comprises providing an aqueous phase thickened by the in situ polymerization of:

(a) about from 0.3 to 10%, by weight, based on said aqueous phase, of monomer selected from at least one of the group consisting of (1) monomers having the formula wherein R is hydrogen, lower alkyl or hydroxyalkyl of up to 4 carbons, inclusive, X is COOH,

O i 3-NH2 where M is alkali metal or ammonium and (2) soluble salts of monovinyl pyridines; and

(b) about from 1 to 30%, based on the weight of (a) of polyethylenically unsaturated monomer polymerizable with (a) having at least two terminal methylene groups.

11. A product of claim 10 wherein (a) is at least one monomer of the formula i CH=OX and (b) is at least one monomer of the formula [A] Y 13 wherein A is selected from at least one of the group consisting of i f CHz=CC CH2=CCH2- and CHFCH, the Rs being chosen independently but from the same group as in (a); Y is a bridging radical to which a plurality of A moieties are bonded by oxygen or nitrogen in Y and n is 2 to 4, inclusive.

12. A product of claim 11 wherein (b) A is n is 2 to 3, inclusive, Y is an aliphatic chain of 1 to 6 carbons to which the A moieties are joined by amido nitrogen or oxygen and the Rs in the (a) and (b) components are hydrogen or methyl.

13. A product of claim 12 wherein the (a) component consists essentially of acrylamide.

14. A product of claim 13 wherein the (b) component consists essentially of N,N-methylenebisacrylamide.

15. A product of claim 12 wherein said oxidizing component consists essentially of at about 65% of ammonium nitrate.

16. A product of claim 15 wherein said fuel comprises about from 10 to 45% of TNT, based on the total Weight of said product.

17. A product of claim 15 wherein said fuel comprises about from 2 to 20% of non-explosive carbonaceous fuel based on the total weight of said product.

References Cited UNITED STATES PATENTS 2,826,485 3/1958 Scalera et a1 14921 XR 3,072,509 1/1963 Barnhart et al. 14960 XR 3,097,120 7/1963 Hoffman et a1. 149-19 3,164,503 1/1965 Gehrig 14918 XR 3,202,556 8/1965 Chrisp 149-60 XR 3,312,578 4/1967 Craig et al. 14960 XR 3,322,583 5/1967 Guthrie et a1. 14919 FOREIGN PATENTS 712,981 7/1965 Canada.

L. DEWAYNE RUTLEDGE, Primary Examiner.

25 L. A. SEBASTIAN, Assistant Examiner. 

1. IN THE PROCESS FOR MAKING WATER-BEARING EXPLOSIVES WHICH COMPRISES BRINGING TOGETHER WATER, FUEL AND AN OXIDIZING COMPONENT CONSISTING ESSENTIALLY OF INORGANIC OXIDIZING SALT, THE IMPROVEMENT WHICH COMPRISES GELLING THE AQUEOUS PHASE OF SAID EXPLOSIVES BY COPOLYMERIZING IN SITU A MIXTURE OF MONO- AND POLYETHYLENICALLY UNSATURATED MONOMERS SOLUBLE AND STABLE IN THE SYSTEM, SAID MIXTURE COMPRISING: (A) ABOUT FROM 0.3 TO 10%, BY WEIGHT, BASED ON THE AQUEOUS PHASE OF MONOMER SELECTED FROM AT LEAST ONE OF THE GROUP CONSISTING OF (1) MONOMERS HAVING THE FORMULA
 10. IN WATER-BEARING EXPLOSIVES COMPRISING FUEL, WATER AND AN OXIDIZING COMPONENT CONSISTING ESSENTIALLY OF INORGANIC OXIDIZING SALT, THE IMPROVEMENT WHICH COMPRISES PROVIDING AN AQUEOUS PHASE THICKENED BY THE IN SITU POLYMERIZATION OF: (A) ABOUT FROM 0.3 TO 10%, BY WEIGHT, BASED ON SAID AQUEOUS PHASE, OF MONOMER SELECTED FROM AT LEAST ONE OF THE GROUP CONSISTING OF (1) MONOMERS HAVING THE FORMULA 